mahon



l. R. MAHON."

PROTRACTOR.

APPLICATION man MAY16,1919.

Patented Apf. 25, 1922.

relates.

JOHN a. Marron, or NEW YORK, N. Y'. j

' 'appicatiqa mea Marie,

citizen ofthe United States and al resident of the borough of Manhattampcity ofiNeW York, in the fcounty of New Yorkand State f ofNeW ,Yorlnihav'e invented certainnew and useful `lmprovements in a .'Pro'tractoi, of which :the following is ya specification.y f

This invention relates toga protractor the n ovel construction. of which comprises ,a pair of .simi-lar* triangulary Y members, vad]` ustably connected at corresponding apeXes, so Athat they can yberrotatively adjusted about said ape-Xes. Y .I In the` accompanying` drawings which eX'- amplify the invention, Fig. 1 shows a plan view'of the protractor with a pair of obtuse triangular? members; F ig. 2 `remesents a section of Fig. 1 on the broken line 2, 2 with some elements in full; Fig. 3 shows a plan viewof anotherform of theprotra'ctor with a pair-of rightangled triangular members; Fig.V 4L isa section of F ig. 3v on the Vbroken line 4, 4f with some Velements in Vfull and Figy shows a sectionalrviewof a modifica- Referring t igs. andfQ'fgapa-ir of equal and obtusev triangular members A and B,

f With their surfacesfinI-the same planes, are

located with the apeXes oftheir obtuse angles at a point C. A fcentral circular; disc 10 is fastened to the triangular member B' by means of the rivets 11. The disc 10 at a portion adjacent to its circumferential edge has formed thereon a scale 12. A slot 15 concentric with the point Gis formed in said disc. A ring 16 has its in uer circumferential edge 17 and its outer circumferential edge 18V perpendicular to the plane of the face thereof, andit is securely fastened` to the triangular member A by ymeans of the rivets 20. An indicatorline 21, marked O' is indicated on the outer face ofthe ring 16. rIhe disc 10 and ring 16 constitute a joint for the members A and B. u

The inner circumferential edge 17 of the ring 16 registers with the outer circumferential edge of the central disc 10. A screw 25.istightly secured inthe triangular member. A, extends through the slot 15, and is provided with the thumb nut 26. A pair of rivets 28 secured to the member B rotatively engage the ring 16.

In Figs. 3 and l the protractor is shown' to comprise the equal right angled triangul l' Specification oi' Letters iatent'.

' larmembers D andE.

` sectional.; viewofa Y bers M andNrespectively similarlt'ofA and are indicatedwith,thelsectional viewgoffa v central fdisc p44 `similar",tof-10, -having 'la lslot Vf1-5 similar to I Atherefrom fthe. sleeve 'bears on thecentral disc-4A. 50 in threaded engagementwith the `screw .catedV parallel to the edge X.

191e1v seriai Nq. 297,534. I

same planes andfsaid membersare -locatedso that their apexes at their right angles`meet at the point H. A central disc `SOWith'- the beveled circumferential edge/31 is fastened to the triangular member E, by means of the rivets The disc BQata portion -ad-l jacent to its circumferential edge hasfformed thereon a scale 33. vlA slot' concentric with the point l-i is-formed ,in said diseBO.

.A .ring 36 Withv thek inner `beveled circumferential; edge 37 is securely fastened to f the triangular member D, by means of the rivets l10. An indicator line Z11 marked '-0 is indi-f A cated on the-outer face ofthe ringBG.. The inner beveled circumferential edge 37 of the rmgiSG registers with thebeveled-ciroumfferentialedgel ofthe centraldisc() and i V therebytheloWer sidefllQof the Vring 36 is maintained in contact Awith the adjacent face ofthe triangularfmember- Inthe m .diiication'shown in Fig, d'5, pair of Vtriangular mem-V .'A Y'screw 146 has formed on' itssh'ankA the flange Y end 48,? VThe screwy is. fastened to the member M by `locating thel thathasV extending flange-47 onthe top face-thereof and rivet@ ing the sleeve end 48 lthereto.V A Washer L1-9 1s carried on the shank of the A thumb'nutv A6 has a cavity 51.

A spring'52 lbears be--Y tween the crown of theca'vity 51 and the screw 46 and Washer`r 19. The thumb lnut 50 with ,itsl

Washer L19 and screw 16 constitute a friction clamp to adjustably .clamp the'central disc lei to the triangular:member M.

Referring to the Figsfl and 2 the triangular members A and Bhave each an obtuse angle of 115 degrees, an acute angleoffQO Y degrees and a third' angle of l5 degrees.

Each'of* the edges X, 'Y and Z can be used as a ruling edge. l, vThe used with the edge X of the fmember'-B bearing against the ruling :edge of av 'T square, atriangleor straight edge. In this instance the member A has itsfepdge X .lo-

A can be rotated up' to vthe left so that its" ruling edges will make. angles of from '0 degrees to degrees WithV theirwpresent p rotractor is preferably y The member l Vangles oif from O to positions, and Vdown to the right so that said ruling edges will make angles ofrfi'om O to l0 degrees withtheir indicated positions. -riilie member B is shown with the ruling edges X, Y and Z and can be moved down to the lett so that its ruling edges willl make u 90 degreesWith their present positions, and upy to that its ruling edges will make angles of from 0 degrees to AO degrees with their present positions. The members are rotated by slightly unscrewing the'thumb scren7 26 or overcoming the tension of the spring 51, when the modification shown in Fig. 5 is used.

By placing the edge X of the triangular member A against a T squarefor the like, and using the edges of the member B the directions of the lines made With the edges L0i: the latter member are reversed i'rom those made with the rulingedges oi* the memberY A, thereby permitting included angles to be drawn With the lilies initially drawn With the ruling edges of the member A. VThe protractor shown in Figs. 3 and L can bev used in a manner similar to that just described, With this modification. Each ot the members D and E can beswung through f angles lfrom 0 degrees to 180 degrees and the edges of the members `can be made to take. corresponding directions.

The construction shown in Figs. l and 2 permits the edges X and X to be a comparatively short dist-ance apart-When they Y are oarallelto each other. Y y Y avingy described myinventionwhat I de-V sire to secure by Letters 1atent and claim is: l. Ina'protractor the combination oic a pair of triangular members each with three the right so Y l pair of Vtriangular members, each With rul-'Y ruling edges, a central disc fastened to one oi the members and adjustably connected to the other member, a ring registering with said central disc fastened to the member that adj ustably carries the disc and bearing on the other member and means to maintain the disc and ring in register With eachr other. 2. ln a protractor the combination or' a ing edges, a central circular disc With a scale adjacent to its circumferential edge fastened to one of the'members, saiddisc having a slot' concentricwith its center, a screw ywith its shank fastened to the second member and extending through said slot, ya thumb nut in the screw to 'clamp theJ disc to said second member, a ring registering .with said disc fastened to said second member, said ring having an index line to'coact With the scale on the central disc and means to rotatively connect said ring With said rst member. i

3. In a protractor the combination oi' a pair of triangular members, each with ruling edges, a central circularv disc with a scale adjacent to its circumferential edge permanently fastened to one of the members, a friction clamp adjustably disc and permanently connected tothe second member, and a ring registering With said disc permanently connected to the sec ond member and rotatively connected to the first member. v f

Y Signed at the boroughV of Manhattan, city of New York, inV the .county 'of New York and State of New `York, this 30th day of April, A. D. 1919.- Y l l f Jointl n. Marion.

connected to said 

